Interfacial Oxidation and Photoluminescence of InP-Based Core/Shell Quantum Dots

Abstract

Indium phosphide colloidal quantum dots (QDs) are emerging as an efficient cadmium-free alternative for optoelectronic applications. Recently, syntheses based on easy-to-implement aminophosphine precursors have been developed. We show by solid-state nuclear magnetic resonance spectroscopy that this new approach allows oxide-free indium phosphide core or core/shell quantum dots to be made. Importantly, the oxide-free core/shell interface does not help in achieving higher luminescence efficiencies. We demonstrate that in the case of InP/ZnS and InP/ZnSe QDs, a more pronounced oxidation concurs with a higher photoluminescence efficiency. This study suggests that a II–VI shell on a III–V core generates an interface prone to defects. The most efficient InP/ZnS or InP/ZnSe QDs are therefore made with an oxide buffer layer between the core and the shell: it passivates these interface defects but also results in a somewhat broader emission line width.

Surface passivation extends single and biexciton lifetimes of InP quantum dots

“…S8 † ). Thus, we attribute this faster XB decay at low HF concentration to the photodegradation of InP, probably due to the formation of an oxide layer around InP QDs 46 which may act as an additional electron trap. With enough amounts of HF (InP@F – 100 μl and InP@F – 300 μl ), this degradation pathway is, however, effectively suppressed, resulting in identical decay dynamics of XB in InP@F – QDs as the untreated InP QDs.…”

III–V colloidal nanocrystals: control of covalent surfaces

“…In addition, III-V QDs suffer from severe oxidation upon exposure to any oxygen sources, owing to the high oxophilicity of elements in groups III and V. [59][60][61] Although the effect of surface oxidation on the optical properties of III-V QDs is still largely un-explored, it is apparent that the oxidized surface obscures atomistic surface investigations. An oxidation-free surface will certainly facilitate a greater understanding of the surface of III-V QDs.…”

Synthesis of In₃₇P₂₀(O₂CR)₅₁ Clusters and Their Conversion to InP Quantum Dots

“…. Surface defects, oxidation, and alloying are critical factors still under intense research that will require significant innovation for optimized InP architectures 19,20,21,22,23,24 . The atomically precise nature of clusters, such as In 37 P 20 (O 2 CR) 51 , makes them ideal platforms for probing the consequences of many post-synthetic surface modifications.…”